Modified coal tar and method for the production thereof



Patented Jan. 30, 1940 UNITED STATES PATENT OFFICE MODIFIED COAL TAB ANDMETHOD FOR THE PRODUCTION THEREOF John Edward Lynn, East Boston, Mass,assignor to Hercules Powder Company, Wilmington, Del.,' a corporation ofDelaware No Drawing.

Application June 22, 1938,

Serial No. 215,223

14 Claims. (Cl. 106-32) and the inertness of coal tar, however, it isused for many things, such as, for example, roofs, roads, etc., eventhough it is realized that it has the drawback above mentioned. Variousattempts have been made in the past to decrease this tendency to flowwith increasing temperature. I

' It has been customary, for example, to add considerable amounts ofother ingredients in the form of fillers, such as, clay, slate flour,and the like, to decrease the tendency to fiow as the temperature rises.It has been found, that the addition of a filler increased the viscosityand the softening point of the resultant mixtureand caused theassumption to be made that the addition of a filler produced aconsiderable decrease in the susceptibility to temperature change.Actually, however, the addition of such fillers results in no decreasein the tendency of a coal tar to fiowwith increasing temperature, butmerely increases the softening point of the coal tar which isanundesirable feature. Furthermore, coal tar itself is brittle at lowtemperature and the addition of the fillers mentioned increases ratherthan decreases the brittleness of the final product.

Now, I have found that I may obviate the disadvantages above cited andproduce a modified coal tar which shows a surprising improvement in theresistance of the coal tar to flow when the temperature increases andwhich has a superior flexibility and improved adhesion at lowertemperatures. More particularly, I have found that these improvedqualities may be imparted to. a refined coal tar by the addition theretoof gasoline-insoluble resin derived from pine wood, together with smallamounts of aluminum chloride. Instead of the aluminum chloride alone, Imay use combinations thereof with basic metal'hydroxides or oxides,among which are, for example, sodium hydroxide, magnesium oxide,potassium hydroxide, calcium hydroxide, zinc oxide, etc., and of these Iprefer usingsodium hydroxide and calcium hydroxide. In the latter casethe amount of aluminum chloride used in modifying the tar maybe reduced.

The gasoline-insoluble pine wood resin I employ for the preparation ofmy improved modified coal tar may be produced, for example, byextracting resinous wood with a coal tar hydrocarbon, removing saidhydrocarbon by-evaporapreparationof my improved modified coal tar tion,leaving a residue comprising a mixture of wood rosin and the new resin,extracting wood rosin from the said residue by a petroleum hydrocarbon,and leaving the new gasoline-insoluble pine wood resin, as is describedand claimed in application," Serial :No. 61,745, filed' January 31, 1936by Lucius C. Hall. I I

The aluminum chloride which I employ for the is preferably in ananhydrous condition. It is well known that aluminum chloride hydrate(A1013: EH20) has the solubility characteristics of an inorganic saltand is unaffected by typical organic solvents, suchas ether, carbontetrachloride, etc. completely hydratedialuminum chloride in themodification of coal tar in accordance with the method herein described,does not produce any significant improvement over an unmodified coal tarof like softening point. However, if the 20 aluminum chloride used,although originally anhydrous, has absorbed a small amount of .water, itwill still be reactive in my. process, al-

though the reactive fraction will only be the anhydrous material stillpresent, the hydrated 5' part acting'merely as an inert filler.Therefore, it is to beunderstood, that where I refer to aluminumchloride in the specification and claims, I mean a product substantiallyin an anhydrous condition.

The coal tar which I use as a starting material 1 for producing myimproved product is a refined coal tar which is a viscous fluid at roomtemperature and which loses about to of its volatile matterwhen heatedto raise the softening point to about 130 F.

I have found that the rate of change of the viscosity characteristic ofmy improved modified I coal tar with temperature is considerably lessthan that of an unmodified tar, resulting in a betterfiexibility at lowtemperatures, promoting better adhesion-at such temperatures, andreducing the fiow as the temperature increases.

Although the complexityof the reactants which go with my improvedcomposition has made it impossible for me to determine its chemicalcom.- position, Iattribute its improved properties to a unique colloidalstructure not possessed by the. I modified coal tars heretoforeproduced.

The following data, for example, indicate that} the volatile loss at 325F. of my modified and an unmodified coal tar control is somewhat greaterfor the former, as shown below. While the difierence is not great, it issufiicient to indi cate' that my modifiedcoal tar evidently possesses Ihave found that the use of this u a unique structure in order to showequally high softening points and at the same time more volatile matterthan the unmodified tars.

Softening Percent Treatment pomt Do Modified".

In proceeding in accordance with my invention I may take a refined coaltar and add thereto from about 2% to about 30%, preferably from about 2%to about 7% of the weight of the refined coal tar, of gasoline-insolubleresin derived from pine wood together with a small amount of aluminum,chloride; or mixtures thereof with basic metal oxides or hydroxides andheat this mixture to about 400 F. to 450 F., While stirringcontinuously. The mixture is cooked at this temperature until a dropletof the mixture cooled on a plate, softens in approximately the sametime, when the plate is gently heated, as an adjacent droplet of anunmodified coal tar control having the softening point desired. Heatingof the mixture at a temperature around 400 F. to 450 F. should beminimized to as. great an extent as possible, because of thevolatilization of aluminum chloride.v Prior to heating, I prefer to makedispersions of both gasoline-insoluble resin derived from pine wood andthe aluminum chloride or 6f aluminum chloride in combination with basicmetal oxides 0r hydroxides, separately in the refined coal tar and thencombine these two and cook the mixture to the desired softening point. Ihave found that I obtain more intimate admixture of the variousreactants when proceeding in this manner, although it is to beunderstood, of course, that other ways of combining the ingredientsprior to cooking are not precluded. For example, gasoline-insolubleresin derived from pine wood and aluminum chloride may be groundtogether and added to the refined coal tar and the mixture then heated.

I have found that it is necessary for gasolineinsoluble resin derivedfrom pine wood and-the aluminum chloride to be reacted together in thepresence of the refined coal tar containing the volatile componentsinorder to produce a modified coal tar havingthe properties of reducedflow at elevated temperatures as well as better flexibility and adhesionatlow temperatures. If gasoline-insoluble resin derived from pine woodis dispersed in one-half the refined coal tar and the aluminum chloridein the other half, and the separate halves then cooked to approximatelythe desired softening point before combining the two products, I findthat there is little or no improvement over a modified coal tar with asimilar softening point. i

. The amount of aluminum chloride or mixtures thereof with thecompounds, before mentioned, which are added to the tar depends on thecharacteristics of the tar and the particular combination of compoundsused. Whether using aluminum chloride alone or various combinationsthereof, as before given, I have found that the total amount, based onthe weight of the coal tar should be from about 0.5% to. about 5.0%.preferably about 1% by weight. I have found, for example, that theamounts, of the compounds volatile examples.

shown in the following table give very satisfactory products when usedin conjunction with about 2%-30%, preferably with about 27% by weight ofcoal tar of gasoline-insoluble resin derived from pine wood, beforeshown.

TABLE H Per cent Aluminum chloride alone about 1 Aluminum chloride 0.94Sodium hydroxide 0.05

Aluminum chloride 0.36 Calcium hydroxide 0.11

In the general procedure outlined above and in the examples which followbelow, the starting material for both the unmodified and modifiedsamples is a refined coal tar which is a viscous fiuid at roomtemperature. For general service work, a coal tar is desired having asoftening point in the range of about 120 F. to 140 F. In following theprocedure in accordance with this invention modified coal tars areproduced having a softening point within this range. In order to have afair comparison between a modified coal tar and an unmodified coal tar,it is necessary to use tars of substantially the same softening point.The unmodified coal tar control samples are, therefore, made bysubjecting the refined coal tar to a similar cooking treatment in orderto drive off the volatile components and raise the softening point to apoint within the above specified range. All comparisons shown in thefollowing examples are thus always made between modified coal tars andunmodified coal tar controls having substantially the same softeningpoint.

Having described my invention in a general way I will now proceed to amore detailed description thereof by reference to the following All.parts shown in these examples are parts by weight.

Example I '212" F. and, While stirring, 0.1 part of sodium hydroxide wasadded and the temperature raised to 300 F. At this point 1.9 parts ofaluminum chloride were slowly added while stirring the mixture and thetemperature was raised to about 425 F.-475 F., and held there for 20minutes, after which the mass was allowed to cool. The softening pointof this modified coal tar by the ring and ball method was 134.4 F. V

A sample of the above modified coal tar when subjected to the Barrettslide test as described in Industrial and Engineering Chemistry 10, 735(1918), a test well known to the art, showed that my modified coal tarflowed 4 inches in two hours at a temperature of 140 F. A sample of theunmodified coal tar control, with the same softening point, (134.6 F'.),run simultaneously, flowed 6 inches in 50 minutes. In the same time thatthe'unmodified coal tar flowed 6% inches, the above modified coal tarflowed only 3 inches, or less than as much. It is apparent ,Six parts ofgasoline-insoluble resin derived from pine wood were-added to 194 partsof refined coal tar, andthis mixture-then-heated to 300 F. Whilestirring this, 2 parts of aluminum chloride were slowly added, thetemperature-then raised to about 425 F. t0475 -F.-, and held there forminutes after which the mass was allowed tocool. The softening point ofthis 1 modified coal tarby the ring and ball method was 131.7 F.

. inches or slightly more than as much as the unmodified tar. The markedimprovement shown by my modified coal tar is again quite apparent.

In this case it should also be noted that greatly improved resistance tofiow is attained with my modified coal tar even though its softeningpoint is slightly lower than the original tar, which is contrary to whatwould be expected.

Example III Thirty-six parts of gasoline-insoluble resin derived frompine wood were incorporated 'in 600 parts of a refined coal tar byraising the temperature sufl'iciently tomelt the resin. Twelve parts ofaluminum chloride were then dissolved separately in 600 parts of thesame tar by warming the latter slightly. These two separately preparedcomponents were then combinedand cooked at a temperature of 400? F.-450F. for

about 20 minutes, producing a modified coal tar having a softening pointof 126.5 F.

A sample of this modified coal tar when subjected to the Barrett SlideTest in the same manner as indicated before fiowed 6 inches in 1'7minutes. An unmodified coal tar control sample witha softening point of127 F. flowed the same amount under the same conditions in 12 minutes.

In order to illustrate the better coldfiow of my improved modified coaltar, a sample of the modified tar as prepared in Example I above and anunmodifiedcoal tar control of about the same softening point weresubjected to a penetration test, using a penetrometer and standardneedle as described in A. S. T. M. Standard Test Method D525.Penetration is expressed as the distance that a standard needlevertically penetrates a sample of the material under known conditions ofloading and is a measure of the consistency of the bituminous material.In the present case the load. was 100 grams applied over a relativelylong period of time in order to increase the accuracy of the test. Thereadings obtained were then calculated to the penetration occurring infive seconds whichis the standard time interval, and are noted inhundredths of a. centimeter.

At 32 F. I found that the needle penetrated the unmodified coal tarcontrol to a depth of 0.03 of a centimeter. At the same temperature, thepenetration of the needle into the coal tar modified as in Example Iabove was 0.09 ofa centimeter. In other words, the penetration of theneedleinto the modified tar was three times as great. This indicatesthat the coal tar modified in accordance with this invention is muchmore fiuid at this low temperature than the unmodified control sample.

It is apparent therefore, that coal tar modified in accordance with thisinvention retains its flexibility better at low temperatures than anunmodified tar of substantially the same softening In the same period,that is 50 minpoint; ''The fact' that the modified tar flows less thanthe unmodified tar at-elevated temperatures' has already been shown.Thus it is seen'that not only does my improved modified coal tar fiowless at-elevated temperatures but it retains its flexibility better atlow temperatures, both being important advantages in the variouspractical applications of'coal tar and which have not been obtained byprior art modified coal-tars; It will be understood-that the examplesabove given-are by way of illustration only, and that the scope ofmy-invention isnot to" be limited th t w J .i a.

What I claim and desire to protect by Letters Patent is: v

1. An improved modified coal tar comprising a refined coal tar modifiedwith gasoline-insoluble resin derived from pine wood and aminor amountof aluminum chloride.

2. An improved modified coal tar comprising a refined coal tar modifiedwith gasoline-insoluble resin derived from pine woodand a minor amountof aluminum chloride and a compound selected from the group consisting:of basic metal oxides and basic metal hydroxides.

3. An improved modified coal tar comprising a refined coal tar modifiedwith gasoline-insoluble resin derived frompine wood and a minor amountof aluminum chloride and sodium hydroxide.

4. An improved modified coal tarcomprising a refined coal tar modifiedwith gasoline-insblw ble resin derived from pine wood and a minor 7amount of aluminum chloride and calcium hydroxide.

5. An improved modified coal tar comprising a refined coal tar modifiedwith about 2% to about 30% by weight of said coal tar ofgasoline-insoluble resin derived from pine wood and with about 0.5 toabout 5% by weight of the coal tar of aluminum chloride. 1 I

I 6. An improved modified coal tar comprising a refined coal tarmodified with about 2% toabout 7% by weight of the saidcoal tar ofgasolineinsoluble resin derived from pine wood and with.

about 1% by weight of said coal tar of aluminum chloride.

7. An improved modified coal tar comprising a refined coal tar modifiedwith about 2% to about 7% by weight of thesaid coal tar ofgasolineinsoluble resin derived from pine wood and with about 1% byweight of said coal tar of a combination of aluminum chloride and acompound selected from the group consisting of basic metal oxides andbasic metal hydroxides. t

8. The method of making an improved coal tar which comprisessimultaneously heating together gasoline-insoluble resin derived frompine wood and a refined coal tar in the presence of aluminum chloride.

9. The method of making an improved coal tar which-comprisessimultaneously heating together a refined coal tar, gasoline-insolubleresin derived from pine wood and alurninum chloride and a compoundselected from the group consisting of basic metal oxides and basic metalhydroxides.

10. The method of making an improved coal tar which comprisessimultaneously heating together derived from pine Wood and aluminumchloride and calcium hydroxide. v p

15;. The method of making an improved coal tar which comprisessimultaneously heating together a refined coal tar, about 2% to about30% by weight of refined coal tar of gasoline-insoluble resin derivedfrom pine wood and about 0.5% to about 5% by weight of the said coal tarof aluminum chloride.

13. The method of making an improved coal tar which comprisessimultaneously heating together a refined coal tar, about 2% to about 7%by weight of refined coal tar of gasoline-insoluble resin derived frompine wood and about 1% of the weight of said coal tar of aluminumchloride. I j

14. The method of making an improved coal tar which comprisessimultaneously heating to-

